Gas-filled grid controlled electronic tube



Sept. 22, 1953 A. w. COOLIDGE, JR

GAS-FILLED GRID CONTROLLED ELECTRONIC TUBE Filed March 23; 1951Inventor-z e o w m M 5 O c. M W. .6 w H m M W Patented Sept. 22, 1953GAS -FILLED GRID CONTROLLED ELECTRONIC TUBE Arthur w. Coolidge, Jr.,Scotia, N. Y., asslgnor to General Electric Company, a. corporation ofNew York Application March 23, 1951, Serial No. 217.262,

' 1 Claim. 1

The present invention relates to electric dis- Y charge devices of thegas or vapor-filledtype, and

particularly to improved devices of this character with respect to theability of the device to conduct large currents and withstand severecommutation duty.

In electric discharge devices of the gaseous type,

it is a. problem to provide constructions which function properly undercertain electrical conditions. For example, to be commerciallysatisfactory, the control electrode must operate consistently to permitinitiation of conduction at the same instant in the anode voltage Wavefor a given voltage of control electrode. Also, the tube must be able toprevent the establishment of a discharge during the inverse voltagecycle. A measure of the ability of a gaseous tube to remainnonconducting immediately following a period of normal conduction isprovided by th commutatation factor of the tube. The commutation factorof a tube has been defined as the product of the rate of current decayin amperes per microsecond just prior to the end of the commutationperiod, and the rate of inverse voltage rise in volts per microsecondjust after commutation is complete.

Recently gas or vapor electric discharge devices, particularly thoseemploying a rare gas filling, have been designed to provide rathercomplete shielding of the anode in order to protect th anode frompositive ion bombardment during the inverse voltage cycle. Close spacingbetween the grid and the anode and between these electrodes in theshielding has also been provided to limit the number of ions alfected bythe anode field at the end of a period of conduction, and to limit thevolume of ions inthe grid anode region.

While these improvements have resulted in good electricalcharacteristics of the tubes, they. have from a manufacturing point ofview been rather expensive and have required a large number of metalparts for the shielding function. The support of thes parts also rendersthe resultin mount somewhat complicated to assemble and less rigid froma mechanical point of View than would be desirable.

It is an important object of the present invention, therefore, toprovide an improved gaseous type of electric discharge device which isimple and rugged in construction and which is capable of carrying largecurrents and exhibits satisfactory electrical characteristics, even incircuits subjecting the devices to severe commutation duty.

Further objects and advantages of my invention will become apparent asthe following description proceeds, referencebeing had to theaccompanying drawing in which the single figure is an elevational viewin section of a gaseous electric discharge device embodying myinvention.

The electric discharge device there illustrated includes a pair ofgenerally cylindrical envelope sections l and 2 of glass or otherinsulating material, having open ends joined together in hermeticailysealed relation by the oppositely extending flanges 3 and 4 of a. gridstructure designated generally by the numeral 5. The grid structure mayto advantage be fabricated from a pair of cup-shaped members brazedtogether in back-to-back relationship, and including central planarportions 6 and l in addition to the flanges 3 and 4. The planar centralportions 6 and I are provided with suitable slots 8, through which theelectric discharge may take place. A suitable grid terminal 5a is joinedto the flanges 3 and 4 of the grid members.

The lower end of the envelope I is provided with a pair of circularbosses 9, to which suitable metal closure members In and l l are sealed.These closure members are of cup shape and are preferably formed of analloy having temperature expansion characteristics matching those ofglass, such as one of the well-known iron-nickel cobalt alloys. Thecathode structure, designated generally by the numeral I2, is supportedfrom the terminals It and H by a pair of conductors l3 and I4, which aresuitably bonded to the members I0 and H. The external terminalconnections for the cathode are provided by a pair of strap terminals I5and I6 secured to the members l0 and II.

The anode is sealed to and supported from the other end of theinsulating envelope section 2. As illustrated, th anode includes agenerally planar and circular action portion ll, formed integrally Witha cylindrical supporting portion [8, the outer end of which is joined tothe envelope section 2 by a sealing ring 19, preferably formed of anironnickel-oobalt alloy. The planar portion of the anode is reinforcedby a heavy circular plate 20, brazed or otherwise secured to the outersurface of the planar portion ll of the anode, and a terminal connectoris provided by a heavy conducting strap 2|.

As will be apparent from an inspection of the drawing, the diameter ofthe supporting portion of the anode is only slightly smaller than theinternal diameter of the flange 4 of the grid, and the envelope portion2. The length of the supporting portion is also sufiicient to space theactive anode surface very closely with respect to a minimum. Theconstruction is much simpler than the internally shielded gaseous tubeswhich have been employed in the past. The large exteriorly exposed anodesurface and the exteriorly exposed grid surfaces facilitate theconduction of a large amount of heat away from these elements.

While I have described a particular embodiment of my invention, it willbe apparent to those skilled in the art that changes and modificationsmay be made without departing from the true spirit and scope of myinvention in its broader aspects, and I aim, therefore, in the appendedclaim, to cover all such changes and modifications as fall within thetrue scope and spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

An electric discharge device of the gaseous discharge type, comprising agenerally planar grid structure, having a pair of circular flangesextending in opposite directions from the outer edge of said gridstructure, a cylindrical envelope sec- 4 tion of insulating materialsealed at one end to one of said flanges, an anode structure including agenerally planar active surface and a cylindrical supporting structurejoined at one end to the outer edge of said active surface and sealed atthe other end to said envelope section, said cylindrical supportingportion extending within said envelope section and supporting said anodein closely spaced relation with respect to the planar surface of saidgrid and the diameter of said supporting portion being only slightlysmaller than the internal diameter of said envelope section and theflange on said grid to enclose a minimum volume of gas between saidanode and grid, a second cylindrical envelope section of insulatingmaterial sealed to the other flange of said structure of said envelopesection and a cathode supported within said other envelope section.

ARTHUR W. COOLIDGE, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,179,601 Smith Nov. 14, 1939 2,367,331 Bondley Jan. 18, 1945FOREIGN PATENTS Number Country Date 492,464 Italy Mar. 10, 1943

